1. Technical Field
This invention relates to the field of crop harvesters and, more particularly, to the way in which the headers of such harvesters are floatingly supported for a relatively light, skimming engagement with the ground as the harvesters are advanced during operation.
2. BACKGROUND INFORMATION
In U.S. Pat. No. 3,832,837 in the name of Burkhart, et al., for example, tension springs are connected between the header and the frame of the machine to provide a measure of lifting force to the header which is less than that required to actually lift the header off the ground but which is adequate to effectively lighten the load which skid shoes of the header exert on the ground during advancement, thereby making it easier for the header to skim over rises and falls in the terrain as the harvesting operation is carried out. When it is desired to raise the header at the end of a crop row or to prepare it for over the road transport, hydraulic cylinders are extended to lift the header relative to the frame, allowing the flotation springs to become more relaxed in the process.
From time to time it may become necessary or desirable to adjust the flotation force provided by the springs. For example, there are times when the operator may want to change the cutting height of the header, which is normally accomplished by adjusting the skid shoes. However, such shift in header height also changes the flotation springs. If the operator desires to maintain the same flotation force as before, he must therefore also make an adjustment to the springs themselves in order to bring them back into the appropriate setting.
Sometimes, field conditions alone may dictate that flotation adjustments be made. For example, when moving from one field to another, the operator may discover a lighter load on the skid shoes is preferred due to rocky conditions or irregular terrain, thereby necessitating adjustment of the spring force.
The extent to which the flotation springs exert a lifting force on the header may be adjusted by applying a wrench to one or more adjusting bolts associated with each bank of tension springs at opposite ends of the header. This can, at times, be a rather tedious and time-consuming operation, and it is somewhat difficult to evenly balance the spring forces at opposite ends of the header so that one of the ends is not receiving a disproportionate amount of lift relative to the other.
Whereas harvesters of the type disclosed in the above-mentioned patent lift their headers by the direct action of hydraulic lift cylinders extending between the stationary machine frame and the header, other commercially available harvesters lift their headers by raising the frame to which the flotation springs are anchored, thus stretching the springs until such time as the weight of the header is completely carried by the springs, whereupon continued raising of the frame causes the header to be carried up by spring force with the rising frame. Adjustment of the flotation force of such springs to vary the extent to which the skid shoes of the header bear against the ground during harvesting operations is carried out in a manner similar to that discussed above with respect to the harvester of U.S. Pat. No. 3,832,837.